Most environmental engineers, accustomed to dealing with clarification of suspensions containing approximately 150 mg/1, find it difficult to comprehend dredged material slurries, in which concentrations often reach 150 grams per liter. However, the same physical forces and conditions govern settling of these thicker suspensions, but concentration effects are very important, and the time scale is much longer. Over the last seven years, Vanderbilt University and the Corps of Engineers' Waterways Experiment Station (WES) at Vicksburg, have studied and described many aspects of the settling behavior of different types of dredged material in confined disposal areas.